The study found that the antimicrobial peptide LL‑37 is naturally produced at much higher levels in skin warts caused by human papillomavirus, suggesting the body’s immune system ramps it up during these infections.

LL-37 is a peptide belonging to the cathelicidin family of antimicrobial peptides. Recent investigations have suggested that the expression of antimicrobial peptides is an important mechanism for resistance to microbial infection. The aim of this study was to determine whether LL-37 is expressed in papillomavirus-infected epidermis from patients with condyloma acuminatum or verruca vulgaris. Biopsy specimens from 3 patients with condyloma and 2 patients with verruca vulgaris and 6 normal skin samples were studied by immunostaining with an antibody specific to LL-37 and control rabbit serum. Western blots were performed on skin extracts from normal skin and verrucae. A large increase in the expression of LL-37 was seen within keratinocytes of all involved samples and in the extracts of verrucae analyzed by Western blot. This study shows the antimicrobial peptide LL-37 is induced within the epidermis during the development of verruca vulgaris. This expression represents a previously unknown immunologic response to papillomavirus infection and may represent an important step in the pathogenesis of this disorder.